Method Of End-to-end Available Bandwidth Measurement

With the rapid development of Internet, the demands of quality of service and reliability become stricter, so when the IP network is running, it is important to find network abnormity and diagnose network error. Available bandwidth measurement is one important part of network measurement. So the measurement of end-to-end available bandwidth in the network has drawn interest of researchers. In addition to the great effect on the application of network audio and video cum network optimization, it drives the development of intelligent agent in the computing grid technology of next generation. Based on a variety of theories, methodologies and principle of the end-to-end available bandwidth, a large number of software, due to over simplified model, the incompleteness of the measurement methods and the constrains from the hardware of the testing equipment, these measurement tools have the disadvantages such as complex testing procedures, unsatisfying testing preciseness and constricted application regions etc.Based on studying many datum, this thesis analyses the existed available bandwidth measurement methods and presents the definition of bandwidth and available bandwidth at first. The measurement of using data packet pairs probing train is a classical available bandwidth measurement method, it can comparatively exactly measures the available bandwidth of the network, whereas experiment indicates, due to the exiting of queue failure, probing train drop, multiple router selection and cross traffic, many measurement methods lose currency. Based on these, we analyses the disadvantages of the packet pairs method, present improved packet pairs method and exponent spacing probing train method. Finally the performances of different algorithm are verified and compared in the NS2 platform which runs under Linux system. The simulation results show that the measurement methods improve the transient performance, decrease the disturbance of the cross traffic, and can obtain more exact value of available bandwidth in shorter interval.